Semiconductor photodetectors are widely used for communication, imaging and sensing. For example, photomultiplier tubes (PMTs) are commonly used due to their extremely high internal photo-multiplication gain of an order of 106 and noise-equivalent-power (NEP) of 0.5×10−15 W/Hz1/2. However, the drawbacks of the PMTs are that that quantum efficiency (QE) is generally low, at about 20%, and PMTs need to be operated at over 1000 V electrical bias, thereby making the system utilizing the PMTs complex. In another example, avalanche photodiodes (APDs) in Si, InGaAs(P) or HgCdTe, offer a gain of ˜100 and NEP in the range of 10−100×10−15 W/Hz1/2 at DC bias of about ˜100 V.
Further, heterojunction bipolar phototransistors (HPTs) and resonant tunneling diodes (RTDs) have also been used as photodetectors. HPTs show responsivity of about 1000 A/W when fabricated in InGaAs/InP material system and RTDs show responsivity of about 10 A/W and 3 dB bandwidth of 1.5 GHz at 1.55 μm.
To obtain photodetectors that offer photon detection with a high gain, sensitivity at low illumination light levels and with better dynamic range of detection, the present disclosure presents a new photodetector design that employs a built-in tunneling structure to perform as an internal gain mechanism for photon detection.